Window reaming and coring apparatus and method of use

ABSTRACT

Window reaming and coring apparatus has a reamer connected in the middle of the tool by mechanical joints which permit the reamer to be displaced substantially parallel to the rest, of the tool body. The apparatus is lowered adjacent a pre-determined zone of interest and mills a parallel window along the edge of an existing wellbore into which the reamer is displaced. Once the reamer is fully displaced laterally into the window, the reamer and coring head can be rotated parallel to the wellbore, in the zone of interest for obtaining and retrieving a crescent-shaped core which has a significant cross section and length, enabling improved analysis of the wellbore lithography.

FIELD OF INVENTION

Embodiments of the invention relate to drilling operations and a tubularworkstring for reaming of parallel windows along the side of a wellbore.More particularly, the window can be used to place and position drillingtools in order to: start entry to a lateral section of the well and toharvest a long core along the wellbore sidewall.

BACKGROUND OF THE INVENTION

It is known to cut windows in a sidewall of a main wellbore to drilloffset or lateral wellbores from the main wellbore and for creating apocket or window from which a core sample may be obtained.

The best-known and most widely used method for redirecting a drill bitoff-center of a wellbore is by first setting a wedge-type device, knownas a whipstock, by means of retaining it to the walls of the wellboreusing slips and friction. A drill bit is then lowered and pushed to theside of the wellbore at the angle of the whipstock to start a sidetrackhole. Typically, windows cut using a whipstock may be rough and maypresent some difficulties when tying back the offset wellbore to themain wellbore's casing or liner. Typically, reaming a window using awhipstock requires multiple trips into the wellbore. Further, the fullwidth and depth of the window can only be achieved at the bottom end ofthe whipstock.

During drilling of wellbores, conventional core samples are often takento obtain information relative to the formations. Typically, coringoccurs at the bottom of the wellbore during the process of deepening thehole. Typically, the process requires that the drill string be trippedout and a coring tool be run in for obtaining the core sample, afterwhich the coring tool is removed and the drill string is run in tofurther deepen the borehole to total depth. The need for multiple tripsinto and out of the wellbore makes conventional coring time consumingand relatively expensive. Further, as the location for obtaining coresamples is selected before drilling through a zone of interest, theformation cannot be assessed using well logging techniques and the likeand therefore the core samples often have little or no value inassessing the wellbore.

Further, conventional wireline coring tools and technologies haveimposed limitations regarding the retrieval of a useful length ofcontinuous core, or can retrieve only very small samples of rock bymeans of trepan drilling or impacting perpendicularly into the wellborewall.

Sidetrack coring tools form independent offset boreholes by projectingbelow a reaming collar or deflection tool. The coring tube may becometrapped in the offset borehole and may not be retrievable therefrom.Further, other problems occur as a result of penetration of zonalinterfaces without means for sealing the offset borehole and formationof short boreholes formed along a curved trajectory which compromise theability to harvest a long, continuous, undisrupted core sampletherefrom.

One form of coring assembly, set forth by Applicant in U.S. Pat. No.5,103,921, suffers from some of the disadvantages of the prior artsystems. A deflection crank at a lower end of a reaming and coring tube,contained within a reaming collar, and a universal ball joint at a topend of the reaming tube permit displacement of a lower end of thereaming tube for reaming a window into the main wellbore wall, afterwhich the reaming tube projects below the reaming collar for cutting anangled offset borehole from which a core sample is obtained.

An improved, cost effective and reliable window reaming and coringapparatus, which is capable of cutting and retrieving long cores havinga sizeable cross-section and which are substantially continuous andrepresentative of the lithography of the main wellbore, is required.Further, the apparatus should be readily tripped in and out of thewellbore without risk of the apparatus becoming stuck during reaming orcoring. Preferably, cutting of the core samples should occur after thewellbore has been drilled and logged to ensure that the samples takenrepresent zones of interest along the wellbore.

SUMMARY OF THE INVENTION

Apparatus and method are provided for milling a substantially parallelwindow or windows into the sidewall of an existing wellbore that iscased or uncased, using a single round trip of the apparatus. A reamer,connected between and upper and lower section of the apparatus by upperand lower lateral displacement means, receives lateral displacementforce therefrom and is displaced laterally against the sidewall formilling the substantially parallel window. The laterally displaced,substantially parallel reamer may then be used to cut and retrieve acore or cores at zones of interest along the sidewall of the wellbore.The cores are crescent shaped, being scalloped or cut from the sidewallof the existing wellbore, are substantially continuous in length andhave a sizable cross section for improved analysis. The length of thecore is significant, being limited only by the length of a coreretaining passage within the reamer. The core having been taken alongthe sidewall of the wellbore accurately reflects the lithography of thewellbore at the zones of interest. Further, as coring can now beperformed after drilling the wellbore, the cores can be cut at zones ofinterest in the wellbore, identified previously by well logging and thelike.

In a broad aspect of embodiments of the invention apparatus for mountingon the end of a drill string having a rotatable distal end in awellbore, the apparatus comprises: a reamer, at least a portion of whichhas a rotatable abrasive reaming tube thereon; a non-rotating lowerlateral displacement means connected to a lower end of the reamer andoperable to displace the reamer between a non-displaced position and alaterally displaced position; and an upper lateral displacement meansadapted for connection to the rotatable distal end of the drill stringand connected to an upper end of the reamer for driveably rotating theabrasive reaming tube and for displacing the reamer between anon-displaced position and a laterally displaced position; and a fluidpassage through the upper lateral displacement means and the reamer forsupplying drilling fluids from the drill string a downhole end of theabrasive reaming tube, and wherein when the lower and upper lateraldisplacement means are in the non-displaced position the reamer andabrasive reaming tube are aligned with the wellbore; and when the lowerand upper lateral displacement means are actuated to the laterallydisplaced position, the reamer and abrasive reaming tube are positionedsubstantially parallel to the wellbore for milling a window in asidewall of the wellbore.

One embodiment of the apparatus is a tubular workstring or toolcomprising three sections: an upper section adapted for connection to arotatable distal end of a drill string, coiled tubing or the like fromsurface, a middle section comprising the reamer for milling the windowand cutting and retaining a core sample therein and a lower section atthe bottom of the workstring. The sections are interconnected by theupper and lower lateral displacement means, which, when actuated,laterally displace and maintain the parallel arrangement of the reameragainst the side of the wellbore. The reamer is equipped with an outerreaming tube clad with an abrasive or abrasive protrusions, such as PDCcutters or the like. The reaming tube is rotatable relative to anon-rotataing inner section or mandrel which is connected to thenon-rotatable upper and lower sections of the apparatus. Rotary motionis transferred to the reaming tube through drive means, located in theupper section. The reaming tube is rotatably supported and retained onthe mandrel by bushings or bearings.

The lower lateral displacement means, laterally displaces the reamingtube via a displacement crank or link which provides lateral force to abottom end of the reaming tube in a particular direction. The lowersection of the apparatus contains actuation means to actuate the lateraldisplacement means. Actuation may be by power generation means, such asby a hydraulic power unit generating hydraulic pressure via anaccumulator, an electric motor, spring pressure or force from amotor-driven linear actuator. Preferably, the link is actuated throughlinear motion from a hydraulic ram powered by a hydraulic unit in thelower section of the apparatus.

The upper section comprises a driveshaft having U-joints so as to enableparallel offset of the reaming tube. The bottom U-joint accommodatestransferring of the drill string's torque to the rotatable reaming tube,provides drilling fluid flow to the reaming tube, and exerts push orpull to the reaming tube and lower section of the apparatus in theparticular direction.

The upper lateral displacement means comprises a spindle, extending fromthe drive means to engage the mandrel. Preferably, the spindle engages abiased socket in an axially shiftable housing to permit lateraldisplacement of the upper end of the reamer in the same direction as thelower end of the reamer. The axis of the socket is shifted similarlywith the lower link action so as to direct the top of the biasingsection in the direction of the lower link action.

To achieve the parallel orientation of the reamer and to avoid ajack-knife effect, the lower and upper lateral displacement meansstraddling the reaming tube are connected through the mandrel.Preferably, the mandrel is a mechanical member running inside theapparatus along the entire length of the reamer and forms the fluidbypass conduit in the reaming tube for providing drill fluid to becirculated through the bottom of the reamer for removing cuttings andcleaning the hole.

In a broad embodiment of a method of use, a method for milling a windowin a wellbore comprises: providing a tool having a non-rotating lowersection and an upper section and a reamer connected therebetween, thetool being positionable in the wellbore and each of the upper and lowersections being actuable between a non-displaced position aligned in thewellbore and a laterally displaced position parallel and offset from thewellbore; and positioning the tool in the wellbore; actuating at leastthe lower section to displace a lower end of the reamer; rotating anabrasive outer surface of the reamer to form a window in a sidewall ofthe wellbore; manipulating the tool uphole and downhole, as necessary,to lengthen the window and forming a parallel window substantiallyparallel to the wellbore; and actuating an upper section to displace anupper end of the reamer into the parallel window so that the reamer ispositioned substantially parallel to the wellbore.

In another broad aspect of the method for obtaining a core sample,wherein the reamer has a non-rotating mandrel extending therealong andhaving a core-receiving passage therein and wherein the rotatingabrasive outer surface further comprises a coring head, the methodfurther comprises: rotating the abrasive reaming tube about the mandrel;lowering the tool downhole from the window and into a zone of interestbelow the window to cut a crescent-shaped core from the sidewall of thewellbore; and receiving and retaining the crescent-shaped core into themandrel's core-receiving passage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial longitudinal section view of a window reamer andcoring apparatus according to an embodiment of the invention, shownhaving an abrasive reaming tube in an aligned position for tripping inor out of a wellbore;

FIG. 2 is a partial longitudinal sectional view according to FIG. 1 andshown having the abrasive reaming tube in a displaced position parallelto an axis of the wellbore;

FIGS. 3 a and 3 b are partial sectional views of an upper section of thereaming and coring apparatus according to FIG. 1 illustrating an upperlateral displacement means, particularly,

FIG. 3 a is shown in the aligned position; and

FIG. 3 b is shown in the displaced position;

FIGS. 4 a and 4 b are partial sectional views of the abrasive reamingtube according to FIG. 1, connected to the upper section and to a lowersection by lateral displacement means, more particularly,

FIG. 4 a is shown in the aligned position; and

FIG. 4 b is shown in the displaced position positioned substantiallyparallel to the wellbore;

FIGS. 5 a and 5 b are partial sectional views of a lower section of thereaming and coring apparatus according to FIG. 1 illustrating a lowerlateral displacement means, more particularly,

FIG. 5 a is shown in the aligned position; and

FIG. 5 b is shown in the displaced position;

FIG. 6 is a perspective view of a lower U-Joint of a drive assemblyaccording to FIGS. 1-4 b, illustrating lodging of a ball in a fluidpassage for fluid actuation of a piston to shift the piston within ahousing to permit lateral displacement of the abrasive reaming tube (thereaming tube omitted for clarity);

FIG. 7 a is a cross sectional view of the abrasive reaming tubeaccording to FIG. 4, along section lines A-A, illustrating a corereceiving passage and a fluid bypass passage, the fluid bypass passagebeing a manufactured conduit;

FIG. 7 b is a cross sectional view of the abrasive reaming tubeaccording to FIG. 4, along section lines A-A, illustrating a corereceiving passage and a fluid bypass passage, the fluid bypass passagebeing a solid structural element having a bore formed therethrough,

FIGS. 8 a and 8 b are cross sectional views of the upper lateraldisplacement means according to FIGS. 3 a-b, illustrating shifting ofthe piston within the socket for displacing the abrasive reaming tubelaterally, more particularly,

FIG. 8 a is shown in the aligned position; and

FIG. 8 b is shown in the displaced position;

FIGS. 9 a-b are cross sectional views of the lower lateral displacementmeans according to FIGS. 5 a-b, illustrating a link for lateraldisplacement of the abrasive reaming tube, more particularly,

FIG. 9 a is shown in the aligned position; and

FIG. 9 b is shown in the displaced position;

FIGS. 10 a-e are schematic views of a reaming operation wherein thereaming and coring apparatus is lowered into the wellbore while rotatinga portion of the abrasive reaming tube, more particularly,

FIG. 10 a illustrates lowering the apparatus into the wellbore, theabrasive reaming tube in the aligned position;

FIG. 10 b illustrates lateral deflection of the abrasive reaming tubeagainst a sidewall of the wellbore adjacent a zone of interest;

FIG. 10 c illustrates reaming of a parallel window in the wall of thewellbore by continuing to rotate the abrasive reaming tube;

FIG. 10 d illustrates a core cut from a bottom of the window andretained in a core retaining passage in the apparatus; and

FIG. 10 e illustrates the apparatus having the abrasive reaming tubealigned in the wellbore, the core retained therein, for removal from thewellbore;

FIGS. 11 a-d are schematic views of a reaming operation according toFIGS. 10 a-c and wherein the window is elongated by raising the reamingand coring apparatus while rotating the abrasive reaming tube, moreparticularly,

FIG. 11 a illustrates lowering the apparatus into the wellbore, theabrasive reaming tube in the aligned position adjacent a zone ofinterest;

FIG. 11 b illustrates lateral deflection of the abrasive reaming tube;

FIG. 11 c illustrates reaming of a parallel window in a wall of thewellbore by continuing to rotate the abrasive reaming tube while raisingand lowering the apparatus; and

FIG. 11 d illustrates positioning the reaming and coring apparatus at abottom of the parallel window to commence coring;

FIGS. 12 a and 12 b are longitudinal cross sectional views of analternate embodiment of the upper displacement means, more particularly,

FIG. 12 a is shown in the aligned position; and

FIG. 12 b is shown in the displaced position;

FIG. 13 is a cross-sectional view of the apparatus in the wellborehaving had a parallel window reamed therein and a crescent-shaped coreretained in the apparatus; and

FIGS. 14 a and 14 b are longitudinal cross sectional views of a lowerend of the abrasive reaming tube illustrating core retaining means, moreparticularly,

FIG. 14 a illustrates a finger biased into the core receiving passageprior to receiving a core; and

FIG. 14 b illustrates the finger biting into or applying force to a corein the core receiving passage for retaining the core therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Having reference to FIGS. 1-11 d, a window reaming and coring apparatus1 is shown for mounting on the end of a drill string having a rotatabledistal end 4. One embodiment is shown schematically in FIGS. 11 a-11 d,wherein the apparatus 1 cuts along a sidewall of a wellbore in aformation for forming a window therein, at least a portion of the windowbeing substantially parallel to the axis of the wellbore and along thesidewall of the wellbore, into which a portion of the apparatus 1 can belaterally displaced and subsequently used for cutting a core sampleadjacent the sidewall of the wellbore.

As shown in FIGS. 1 and 2, the apparatus 1 comprises a reamer 10comprising a rotatable and abrasive reaming tube 11, the reaming tube 11having a bore 2 and a non-rotatable mandrel 12, extending along the bore2. The rotatable reaming tube 11 is clad with cutting elements 13, suchas PDC buttons or the like, over at least a portion of an outer surface3 of the rotatable reaming tube 11.

An upper section 20 of the apparatus 1 comprises upper lateraldisplacement means 21 which are adapted for connection to the drillstring's rotatable distal end 4 through drive means 30 for driveablyrotating the abrasive reaming tube 11 and to the non-rotatable mandrel12 of the reamer 10 for urging at least an upper end 14 of the reamer 10laterally, between an aligned, non-displaced position and a laterallydisplaced position.

A lower section 40 of the apparatus 1 comprises non-rotating lowerlateral displacement means 41 connected to a lower end 15 of thenon-rotatable mandrel 12 and operable to laterally displace at least abottom end 16 of the reamer 10.

Before the upper and lower displacement means 21,41 are actuated, and asshown in FIGS. 3 a, 4 a and 5 a, the apparatus 1 is substantially linearand lies within a wellbore 100; After the upper and lower displacementmeans 21,41 are actuated, the reamer 10 is laterally displaced from thewellbore 100, including up to the extent shown in FIGS. 3 b, 4 b and 5b.

More particularly, the reamer 10 is actuable between a non-displacedposition aligned with the wellbore (FIGS. 1 and 4 a) and a laterallydisplaced position offset from the wellbore (FIGS. 2 and 4 b). In thenon-displaced position, the reamer 10 is aligned with the upper andlower sections 20,40 of the apparatus 1, for running the apparatus 1into an existing wellbore 100. In the laterally displaced position, aleast a portion of the reamer 10 is laterally displaced from the upperand lower sections 20,40, and preferably the entire reamer 10 islaterally displaced to a position aligned substantially parallel to acommon axis of the upper and lower sections 20,40.

In operation, as shown in FIGS. 10 a-e and 11 a-d, the apparatus 1 islowered into the wellbore 100 to a position adjacent a zone of interest(FIGS. 10 a, 11 a), such as immediately above the zone of interest. Atleast the lower displacement means 41 is actuated to cause the abrasivereaming tube 10 to be displaced laterally against a sidewall 101 of thewellbore 100 (FIGS. 10 b,11 b). Displacement force, such as hydraulic ormechanically biased force, results at the upper lateral displacementmeans 21 and with compressive force applied through the drill stringacts to urge the upper displacement means 21 to the laterally displacedposition. The upper displacement means 21 orients the reamer 10 to thedisplaced position. The rotatable reaming tube 11, supported andretained by bushings or bearings on the mandrel 12, is rotated by thedrive means 30 to cause the abrasive reaming tube 11 to ream a pocket orwindow 102 in the sidewall. Fluid, such as drilling mud, is conductedthrough a main fluid passage 55 extending through the upper lateraldisplacement means 21 of the apparatus 1 and exits through fluid ports17 at the bottom end 16 of the reamer 10 to remove cuttings (not shown)generated from the reaming process and clean the wellbore 100. For someoperations, a short angular window (FIGS. 10 b and 11 b) is sufficientsuch as to enable re-entry and drilling which is deviated from theoriginal wellbore.

In an operational embodiment to form parallel window 202, as shown inFIGS. 10 a-10 c, the apparatus 1 can be positioned, displaced, androtated to ream and extend the length of the window 102. The window 102is extended in length to form parallel window 202 which is sufficientlylong and deep enough to permit maximum displacement of the upper andlower displacement means 21,41 and the reamer 10.

Optionally, to lengthen the Window 102, and as shown in FIG. 11 c, theapparatus 1 can be positioned, displaced and then lifted and lowered, asnecessary during reaming to backream the side wall 101 for extending thelength of the window 102. Preferably, the window 102 is lengthened toform a parallel window 202 which is sufficiently long and deep enough topermit maximum displacement of the upper and lower displacement means21,41. In the parallel window 202, the reamer 10 can be displaced so asto align substantially parallel to the axis of the wellbore 100.

As shown in both FIGS. 10 c and 11 d, once the reamer 10 is positionedparallel to the axis of the wellbore 100, a coring operation may beginby advancing the apparatus 1 for cutting and receiving a core therein.

In a preferred embodiment of the invention, as shown in FIGS. 3 a and 3b, the upper section 20 of the apparatus 1 further comprises an upholeportion 22, which remains aligned in a wellbore 100 pivotally connectedthrough the drill string's distal end 4 to a driveshaft 23, which ispivotally and driveably connected to the rotatable abrasive reaming tube11 of the reamer 10.

The driveshaft 23 comprises an upper U-joint 31 being driveablyconnected to the uphole portion 22 and a bottom U-joint 32 beingdriveably connected to the rotatable outer surface 11.

The bottom U-joint 32 enables the reamer 10 to be operable between thealigned position and the displaced position relative to the upholeportion 22. Axial compressive forces and rotation from the upholeportion 22 are transferred to the rotatable abrasive reaming tube 11through the driveshaft 23 such as those imposed by the drill string (notshown) connected to the uphole portion 22.

As shown in FIGS. 1, 2, 6 and in greater detail in FIGS. 8 a-b, theupper displacement means 21 comprises a non-rotating housing 50connected to an upper end of the mandrel 12 adjacent the driveshaft 23for aligning the driveshaft 23 in the non-aligned position andmisaligning the mandrel 12 from the driveshaft 23 in the laterallydisplaced position.

In a preferred embodiment, the non-rotatable housing 50 is axiallymoveable within the reaming tube 10 between an uphole position and adownhole position. The abrasive reaming tube 11 is rotatable relative tothe housing 50. The housing 50 is operable to vary lateral force onto aspindle 33 extending downwards from the bottom U-joint 32 and therebylaterally displace the upper end 14 of the reamer 10.

The housing 50 further comprises a biased ramp or socket 51 for engagingand displacing the spindle 33, the socket 51 being angled to achieve adesired direction of lateral displacement to enable lateral movement ofthe spindle 33 thereon as the housing 50 is actuated to shift from theuphole position to the downhole position. The spindle 33 remains freelyrotatable in the socket 51 so as to permit rotation of the rotatableabrasive reaming tube 11 by the drive means 30.

In one embodiment, for shifting the housing 50 from the uphole positionto the downhole position, a passage 52 is formed through the bottomU-joint 32 and spindle 33. Further, a restricted fluid passage 53 isconnected between the housing 50 and a fluid bypass conduit 60 formed inthe mandrel 12 of the reamer 10. In operation, and to aid in shiftingthe housing 50 from the uphole to the downhole position, a plug or smallball 54 is dropped from surface into the fluid flowing through theapparatus 1. The small ball 54 passes through the passage 52 in theU-joint and spindle 32,33 and lodges in the main fluid passage 55between the housing 50 and the reamer 10, the blockage creating apressure differential which acts on the housing 50, like a piston, toshift the housing 50 to the downhole position and to divert the flow offluids to the restricted fluid passage 53 and into the fluid bypassconduit 60.

Further, as shown in FIGS. 5 a and 5 b, the lower section 40 of theapparatus 1 comprises a downhole portion 42 which remains aligned in thewellbore 100 and an uphole portion 43 which is operable between thealigned position and the displaced position. In the preferredembodiment, as shown in FIGS. 1, 2, 5 a-5 b and in greater detail inFIGS. 9 a and 9 b, the lower lateral displacement means 41 comprises alink 42 connected to the lower end 16 of the reamer 10 and moreparticularly to the mandrel 12 of the reamer 10.

The fluid bypass conduit 60, shown in FIGS. 7 a and 7 b, extends fromthe top end 14 adjacent the housing 50 to the bottom end 16 of thereamer 10 and is non-rotating. The conduit 60 acts as a structuralmember to connect the non-rotating upper lateral displacement means 21generally to the non-rotating lower lateral displacement means 41 and toassist in achieving parallel orientation of reamer 10 and to assist inavoiding a “Z” jack-knife effect. The fluid bypass conduit 60 may be amanufactured conduit as shown in FIG. 7 a or a solid structural memberhaving a bore formed therethrough as shown in FIG. 7 b. The rotatablereaming tube 11 is supported and retained thereon by bushings andbearings.

The link 43 is connected at a first point 44 to actuation means 45positioned in the uphole portion 42 of the lower section 40 of theapparatus 1. More particularly, the link is connected to a ram 46 whichmay be actuated by hydraulics, an electric motor, an accumulator or alinear actuator or the like. Further, the link 43 is connected at asecond point 47 to the bottom end 15 of the mandrel 12 of the reamer 10and pivotally at a third point 48 to the uphole portion 42 of the lowersection 40 of the apparatus. The link 43 is manipulated by the ram 46,when actuated, to rotate about the third point 48 to displace the bottomend 16 of the reamer 10, laterally.

In the preferred embodiment, when hydraulic pressure is applied to theram 46, the linear motion of the ram 46 pivots the link 43 resulting inradial displacement of the bottom 16 of the reamer 10, thus anchoringthe apparatus 1 inside of wellbore 100 and exerting perpendicular forceagainst the sidewall 101.

Having reference to FIG. 13, the extent of the maximal displacement ofthe reamer 10 is limited by the extent of motion of the upper and lowerdisplacement means 21,41 and is preferably sized to obtain the maximumthickness of the core sample while still maintaining the fluid bypassconduit 60 therein. More preferably, the maximum displacement is aboutor greater than one half the diameter of the reamer 10 resulting in anoblong shaped wellbore 100 at the window 102. Alternately, in anembodiment of the invention as shown in FIGS. 12 a-b, the upper lateraldisplacement means 21 may comprise a splined housing 56 formed about thebottom U-joint 32 which is axially shiftable from an uphole position toa downhole position on a splined inner surface 57 of an upper portion ofthe reaming tube 10. A wedge 58 is positioned below the bottom U-joint32 and the spindle 33 extending therefrom. As load is applied to thedrill string (not shown), the splined housing 56 and bottom U-joint andspindle 32,33 are shifted to the downhole position and the spindle 33 isdriven down the wedge 58 to displace the upper end 14 of the reamer 10,laterally.

Optionally, the upper and lower lateral displacement means 21,41 can beactuated by applying weight onto the drill string (not shown). In orderto actuate in this manner, the lower section 40 of the apparatus 1 mustbe first temporarily anchored in the wellbore 100 using anchors orpackers and the like. Alternately, a tailpipe piece may be added to thelower section 40 of the apparatus 1 for bottoming in the wellbore 100.Once anchored, weight applied to the apparatus 1 will cause thedisplacement means 21, 41 to be actuated and initiate the process offorming a window 102. In order to continue to core, once the reamer 10has been displaced, the anchors must be released to permit uphole ordownhole reaming or coring movement of the apparatus 1.

Further, in certain circumstances reactive torque may be produced. Thedrill string (not shown) can be set on the bottom of the wellbore 100 toresist downhole and rotary forces. Otherwise, in order to initiate andmaintain the displacement of the reaming tube and hold reactivetorque-generated forces induced by rotary motion, the lower section canbe equipped with apparatus such as anchors or packers for retaining thebottom section in relation to the wellbore.

As shown in FIGS. 10 d and 10 e and in a preferred operation, once theparallel window 202 has been reamed and the reamer 10 is fully displacedlaterally relative to the remainder of the apparatus 1 and the wellbore100, a core sample 110 may be cut and retained therein.

As shown in FIGS. 4 a-b, 7 a-b, 9 a-b and 13, the rotatable abrasivereaming tube 11 of the reamer 10 comprises the mandrel 12, containingthe fluid bypass conduit 60 and a core receiving passage 61 formedtherein. The core receiving passage 61 is crescent-shaped to correspondwith a crescent-shaped core 110 cut from the sidewall 101 of thewellbore 100 as the reamer 10 advances therealong (FIG. 13). Forceapplied to the apparatus 1 through the drill string and rotation of therotatable abrasive reaming tube 11 cuts the crescent shaped core 110which is received into the core receiving passage 61 as a continuouscore 110. The length of the core 110 is limited only by the length ofthe core receiving passage 61 and therefore the core 110 can be ofsignificant length. During the coring process, fluid which has beendiverted from the housing 50 into the fluid bypass conduit 60 exitsthrough fluid ports 62 at the bottom end 15 of the reamer 10 into thewellbore 100 for cleaning debris resulting from the coring and forcooling the coring head 63.

Preferably, a diamond core-head 63, is fitted to a bottom face 17 of thereaming tube 10 for cutting the core 110. The coring proceeds at abottom 103 of the window 102 by pushing the apparatus 1, rotating theabrasive reaming tube 11 and circulating fluid therethrough.

With reference to FIGS. 14 a and 14 b, core retaining means 70 arepositioned adjacent a bottom end 64 of the core-receiving passage 61 forretaining the core 110 therein. In a preferred embodiment, the coreretaining means 70 is a finger 71 biased outwardly by a spring 72 intothe core receiving passage 61. The core 110, as it enters the passage61, forces the finger 70 to rotate uphole against a wall 65 of the corereceiving passage 61. Once the core 110 is fully received into the corereceiving passage 61, the biased finger 70 bites or otherwise exertsforce onto the core 110, retaining the core 110 in the core receivingpassage 61.

Alternately, the core retaining means 70 may be a slip or dog (notshown) set in the wall 65 of the core receiving passage 61 and biasedoutwardly into the core receiving passage 61.

Once the core 110 has been cut, received and retained in the corereceiving passage 61, the lower displacement means 41 are actuated toretract the reamer 10, containing the core 110, into alignment with theaxis of the wellbore 100. Tension applied to the drill string causes theupper displacement means 21 to realign. Once aligned, the apparatus 1 islifted to surface where the core 110 can be retrieved therefrom foranalysis.

1. Apparatus for mounting on the end of a drill string having arotatable distal end in a wellbore, the apparatus comprising: a reamer,at least a portion of which has a rotatable abrasive reaming tubethereon; a non-rotating lower lateral displacement means connected to alower end of the reamer and operable to displace the reamer between anon-displaced position and a laterally displaced position; and an upperlateral displacement means adapted for connection to the rotatabledistal end of the drill string and connected to an upper end of thereamer for driveably rotating the abrasive reaming tube and fordisplacing the reamer between a non-displaced position and a laterallydisplaced position; and a fluid passage through the upper lateraldisplacement means and the reamer for supplying drilling fluids from thedrill string a downhole end of the abrasive reaming tube, and whereinwhen the lower and upper lateral displacement means are in thenon-displaced position the reamer and abrasive reaming tube are alignedwith the wellbore; and when the lower and upper lateral displacementmeans are actuated to the laterally displaced position, the reamer andabrasive reaming tube are positioned substantially parallel to thewellbore for milling a window in a sidewall of the wellbore.
 2. Theapparatus of claim 1 wherein the abrasive reaming tube has a bore andthe reamer further comprises a non-rotating mandrel extending along thebore of the abrasive reaming tube, the abrasive reaming tube beingrotatable about the mandrel, and the lower lateral displacement means isconnected to a lower end of the mandrel.
 3. The apparatus of claim 2wherein the upper lateral displacement means further comprises: adriveshaft adapted for pivoting connection to the rotatable distal endof the drill string and pivotally and driveably connected to therotatable abrasive reaming tube; and a non-rotating housing connected toan upper end of the mandrel adjacent the driveshaft and engagabletherewith for aligning the mandrel with the driveshaft in thenon-displaced position and misaligning the mandrel from the driveshaftin the displaced position.
 4. The apparatus of claim 3 wherein: thedrive shaft further comprises a lower universal joint having a spindleprojecting therefrom for relative rotational coupling with thenon-rotational housing, and the non-rotating housing further comprises aramp for engaging the spindle wherein relative axial movement of thespindle and the housing laterally displaces the spindle for alignment ormisalignment of the driveshaft and the mandrel.
 5. The apparatus ofclaim 4 wherein the housing is hydraulically actuable between an upholeand a downhole position for moving the ramp and displacing the spindle.6. The apparatus of claim 4 wherein the bottom universal joint isaxially movable between an uphole and a downhole position relative tothe ramp for displacing the spindle.
 7. The apparatus of claim 6 furthercomprising a splined connection between the lower universal joint andthe abrasive reaming tube for enabling rotatable drivable connection andaxial movement therebetween.
 8. The apparatus of claim 2 wherein thenon-rotating mandrel further comprises: a core-receiving passage forretaining a core therein; and a fluid bypass conduit, wherein when thereamer is in the displaced position and when the drill string movesdownhole in the wellbore, the core is received into the core-receivingpassage and drilling fluids are supplied to the downhole end of theabrasive reaming tube through the fluid bypass conduit.
 9. The apparatusof claim 8 wherein the abrasive reaming tube further comprises a corehead positioned at a lower end of the abrasive reaming tube for cuttingthe core when rotated, the core being received into the core-receivingpassage as the reamer is moved downhole.
 10. The apparatus of claim 9wherein: the core-receiving passage is crescent-shaped and the fluidpassage is positioned axially within the mandrel; and lateraldisplacement of the abrasive reaming tube is limited for cutting acrescent-shaped core, sized to be retained within the crescent-shapedcore-receiving passage.
 11. The apparatus of claim 8 further comprisinga core retainer positioned adjacent a lower end of the core-receivingpassage for retaining the core therein.
 12. The apparatus of claim 11wherein the core retainer is a finger biased between a non-engagedposition for permitting receipt of the core thereby and into thecore-receiving passage and an engaged position for restricting at leasta portion of the core-receiving passage for retaining the core therein.13. The apparatus of claim 2 wherein the lower lateral displacementmeans further comprises: a lower section positioned in the wellbore; anda link having a first point of connection to an actuator in the lowersection, a second point of connection in the lower section about whichthe link pivots, and a third point of connection to the lower end of themandrel, wherein when the actuator actuates the first point ofconnection, the link pivots about the second point of connection forlaterally displacing the mandrel and the abrasive reaming tube.
 14. Theapparatus of claim 13 wherein the actuator is selected from the groupcomprising hydraulics, accumulator, electric motor, spring pressure andmotor-driven linear actuator.
 15. The apparatus of claim 13 wherein thelink is actuated through relative movement of the drill string and thelower section
 16. The apparatus of claim 15 further comprising an anchorfor temporarily anchoring the lower section in the wellbore.
 17. Amethod for milling a window in a wellbore comprising: providing a toolhaving a non-rotating lower section and an upper section and a reamerconnected therebetween, the tool being positionable in the wellbore andeach of the upper and lower sections being actuable between anon-displaced position aligned in the wellbore and a laterally displacedposition parallel and offset from the wellbore; and positioning the toolin the wellbore; actuating at least the lower section to displace alower end of the reamer; rotating an abrasive outer surface of thereamer to form a window in a sidewall of the wellbore; manipulating thetool as necessary to lengthen the window and forming a parallel windowsubstantially parallel to the wellbore; and actuating at upper sectionto displace an upper end of the reamer into the parallel window so thatthe reamer is positioned substantially parallel to the wellbore.
 18. Themethod of claim 17 wherein the reamer has a non-rotating mandrelextending therealong and having a core-receiving passage therein andwherein the rotating abrasive outer surface further comprises a coringhead, the method further comprising: rotating the abrasive reaming tubeabout the mandrel; lowering the tool downhole from the window and into azone of interest below the window to cut a crescent-shaped core from thesidewall of the wellbore; and receiving the crescent-shaped core intothe mandrel's core-receiving passage.
 19. The method of claim 17 whereinthe tool manipulating step further comprises lowering the tool forelongating the substantially parallel window.
 20. The method of claim 17wherein the tool manipulating step further comprises lifting andlowering the tool uphole and downhole for backreaming and elongating thesubstantially parallel window.
 21. The method of claim 17 wherein alower end of the non-rotating mandrel is connected to the lower section,and wherein actuating of at least the lower section of the reamerfurther comprises: laterally displacing the lower end of the reamerrelative to the lower section; and orienting the upper end of the reamerupon laterally displacing the upper end of the reamer relative to theupper section for displacing the reamer into the parallel window.